STL for C++ Programmers

Although the primary focus is not Linux, his many excellent examples are easily adapted to the g++ environment in Linux 2.0++.

Author: Leen Ammeraal

Publisher: John Wiley

Price: $49.99

ISBN: 0-471-97181-2

Reviewer: Bob Adkins

Good news—STL, Standard Template Library, is alive and well
on Linux. Leen Ammeraal demonstrates this as well as his
considerable skills as a master teacher in STL for C++
Programmers. Although the primary focus is not Linux,
his many excellent examples are easily adapted to the g++
environment in Linux 2.0++ (his examples adapted for Linux can be
found at http://www.cwareco.com/download.html. Ammeraal writes
concise yet thorough explanations on each aspect of using
STL.

What is STL?

STL started in the 1970s with Alexander Stepanov's ideas
about designing general algorithms. Stepanov, together with Meng
Lee, took these ideas to HP and developed the first C++ based STL.
By 1994, STL was accepted into the C++ draft standard by the
ANSI/ISO C++ standards committee.

STL distinguishes general algorithms from the more
specialized data and methods encapsulated by ordinary abstract data
types. In this way, complex and powerful algorithms can be
implemented independently of the data to which they are applied,
allowing for generalization and reuse of these algorithms. In STL
more familiar object abstraction is reserved for data and methods.
These are then tailored and bound to the characteristics of their
underlying container type such as sequence containers and
associative containers. Examples of this distinction with respect
to sequence containers, such as vector objects, are begin, end and
insert. These methods access and manipulate the underlying data of
the vector container class. However, these methods are specific to
the treatment of the data and should not be confused with more
general algorithms such as find,
sort and other advanced numeric
algorithms (e.g., accumulate or inner product). General algorithms
are a kind of method abstraction in contrast to more traditional
data abstraction.

STL on Linux: What's broken. What's not.

STL support has been available on Linux since GNU's libg++
2.6.2. Now with release 2.7.2.1, the library is quite usable for
most major features with the exception of name space scoping. There
are minor differences with other implementations, such as Borland's
BC5 environment, but these differences mostly concern header naming
conventions. There is also a curious problem with
fstream which involves an
unexpected file access mode default.

g++ 2.8.0 will offer a more complete STL based on newer code
from SGI and a complete redesign of the compiler's template
implementation. Unfortunately, g++ 2.8.0 is not expected to fix the
problems with using name spaces.

Overview

From the beginning Leen Ammeraal presents a quick and
practical startup for the STL beginner. He then explains how to use
the sequence containers (vectors, lists and deques), the
associative containers (sets and maps) and, later, examines
containers derived from these basic types such as stacks, queues
and priority queues. As a simple application, he shows how to to
build a telephone directory using associative map containers.
Later, he demonstrates a more complex map application, called a
concordance, which produces a line-oriented index of all words in a
text file. He also shows function objects which can be used to
build custom ordering relationships among the elements of a
container. He moves on to algorithms and the practical details of
STL's generic algorithms for manipulating sequences and for
sorting. He demonstrates the built-in numeric algorithms which make
STL attractive for implementing statistical analysis such as the
Least Squares Method.

How Big Can You Count?

As his final chapter, Ammeraal presents a wonderfully fun
example of “Very Large Numbers”. Here Ammeraal uses STL to
calculate pi to an arbitrarily large number of digits. Ammeraal
exploits the power of STL to reduce the implementation complexities
of defining and operating on extremely large numbers. He notes
that, thanks to the STL's vector container, this version is
“simpler and more elegant” than an earlier solution he presented
in his book Algorithms and Data Structures in
C++.

For added spice, I modified his program to generate a
histogram of the digits computed for pi. At 100,000 places, digit
“1” is a very slight favorite. Moreover, with this example Linux
shows its strength. After turning on full g++ optimization, I was
able to calculate these 100,000 digits in just under 20 minutes.
Under DOS/Windows, Ammeraal indicated that this same calculation
took several hours using BC5.

Bob Adkins
is a software engineer and CEO of
cWare, Inc., a software development company specializing in Web
content distribution using database technologies under Linux and
other Unix platforms. For the past several years Bob has moved
proprietary systems to more open, flexible and collaborative
software solutions. Bob enjoys traveling to Europe and India where
he finds that Linux together with Web information and commerce
applications have the potential to level the international playing
field for rich and poor countries alike. He can be reached via
e-mail at cwareco@erols.com.

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